Composite panel for armor shielding of vehicles

ABSTRACT

Armor panel comprising an aluminium alloy plate wherein:
         a) said aluminium alloy has the following chemical composition expressed in percentages per weight:   5.1%≦Zn≦9.7%   1.5%≦Mg≦2.9%   1.2%≦Cu≦2.1%   Si≦0.4%   Fe≦0.5%   Mn≦0.3%   Cr≦0.28%   Ti≦0.2%   Zr≦0.15%   b) said plate comprises a face oriented towards the shocks and a face opposite said face oriented towards the shocks coated with a composite reinforcing layer comprising reinforcing fibres or bands with high ballistic protection performance, typically made of high mechanical performance glass, aramid or high performance polyethylene.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to FR 13002111.6 filed Apr. 22, 2013the content of which is incorporated herein by reference in itsentirety.

BACKGROUND

1. Field of the Invention

The invention relates to the manufacture of armor shielding panels forthe protection of vehicles from perforating projectiles and fragmentsprojected during an impact.

2. Description of Related Art

In general, an armor shield comprises a metal panel typically made ofsteel, aluminium, titanium or alloys of these metals. Such panelsusually have an excellent capacity for absorption of the kinetic energyof the perforating projectile during an impact. However, in particularif they are made of steel or a titanium alloy, such panels are heavy andconsequently have a low efficiency in terms of energy absorptionrelative to the weight transported by a vehicle. Titanium alloy panelsusually give the best armor shielding protection but they are veryexpensive and heavy.

The armor shielding panel has a face exposed to impacts and a rear face.When there is an impact on a metallic armor panel, the armor-piercingprojectile might be stopped completely in the panel but damage to therear face of the panel can cause the formation of fragments which canbecome more dangerous than the projectile stopped by the panel when theyare violently ejected from the panel (towards the inside of thevehicle).

Composite panels have been developed that have a greater projectilestopping capacity and lower sensitivity to fragmentation, thus givingbetter performances relative to the weight transported by the vehicle.But these are composite products comprising ceramic products placed onthe face exposed to shocks of a support plate, itself composite, usuallybased on carbon, glass and polymers with a high molecular weight. Suchproducts are very expensive.

The efficiency of armor panels is usually characterised by two types oftests. The first test is designed to quantify their capacity to stoppiercing projectiles. This is referred to as “AP” (“Armour Piercing”)and characterises the resistance to perforation. The second test isdesigned to quantify their capability to withstand the impacts offragmented debris. This second type of test is referred to as “FSP”(“Fragment Simulated Projectiles”). During these tests, the armor panelsare the target of different shaped projectiles (spindle shape for the APtest, larger and more squat form projectiles for FSP tests). In eachtype of test, several projectile geometries are used depending on thethickness of the tested panel and the nature of the threats that saidarmor panel is designed to protect.

For both tests, the capacity to stop projectiles and absorb theirkinetic energy without emitting dangerous debris is quantified by avelocity V50 that is defined for example in standard MIL-STD-66; V50 isthe average velocity reached by projectiles at the time of the impactobtained using an equal number of results with the highest partialpenetration velocities and results with the lowest complete penetrationvelocities, the velocity being imposed within a specified range.

In general, the material from which the armor panel is made rarely has agood AP-FSP compromise, regardless of whether it is a ceramic, steel, analuminium alloy or titanium alloy. When it has good resistance to armorpiercing, its FSP resistance is often mediocre. Conversely, a materialwith good FSP resistance often has mediocre AP resistance.

Patent application US2011/0252956 discloses metallic armor panelscomposed of at least two layers of different aluminium alloys that aremetallurgically bonded together. The intimate metallurgical bond betweenthese two layers typically results from transformation procedures suchas co-rolling, multi-layer casting, or casting to obtain a controlledgradient of the concentration of an element such as magnesium within theplate thickness. Alloys are chosen and positioned within the platethickness such that one alloy gives the plate good resistance toperforation and the other gives it good FSP resistance. However, makingsuch panels requires the use of complex and expensive processes.

SUMMARY

The applicant attempted to develop a armor shielding system particularlyadapted to fast vehicles such as military vehicles, typically on wheels,with better efficiency in terms of AP and FSP protection relative to thetransported weight, that is easier to make and less expensive than knownproducts.

A first purpose of the invention is a armor panel comprising analuminium alloy plate characterised in that:

a) said aluminium alloy has the following chemical composition expressedin percentages per weight:

5.1%≦Zn≦9.7%

1.5%≦Mg≦2.9%

1.2%≦Cu≦2.1%

Si≦0.4%

Fe≦0.5%

Mn≦0.3%

Cr≦0.28%

Ti≦0.2%

Zr≦0.15%

the remainder being aluminium and inevitable impurities, the content byweight of each element being less than 0.05%, and the sum being lessthan 0.15%;

b) said plate comprises a face oriented towards the projectiles and aface opposite said face oriented towards projectiles coated with acomposite reinforcing layer comprising reinforcing fibres or bands withhigh mechanical performance that confers a high ballistic protectioncapability on them. Such reinforcing fibres or bands with a highballistic protection capability may be made from one or severalmaterials belonging to the group including:

glass with high mechanical performance such as R, H, S glass orpreferably S2 glass;

aramids, preferably para-aramids such as Kevlar®;

High Performance PolyEthylenes (HPPE) or Ultra-High Molecular WeightPolyEthylenes (UHMWPE or UHMW), that are strongly oriented polyethylenesin the form of fibres, threads or bands, for example Tensylon®.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-4 depict embodiments as described herein.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Advantageously, said composite reinforcing layer comprises one orpreferably several single-directional or woven fabrics made from threadscomprising fibres with a high ballistic protection capability.

The threads or bands are preferably impregnated with a thermoplastic orthermosetting resin, typically a modified PVB (polyvinyl butyral)phenolic resin. The fabrics may be made by weaving several weaves(single-directional, basket weave, fabric stiffener, etc.). Thecomposite reinforcing coating is obtained for example by stacking thefabrics on each other and then compressing them hot.

When values or ranges are listed herein, the value itself is included.For example, “more than X” can also include X.

The term “plate” is used to refer to a flat product that may actually bea sheet or a plate with a thickness of more than 5 mm, preferably morethan 20 mm, typically close to 20-30 mm. The width/thickness ratio ofthe plate is preferably but not necessarily more than 10. The thicknessof the composite panel is typically less than 50 mm, preferably lessthan 40 mm and it has a mass per unit area less than 125 kg/m²,preferably less than 110 kg/m², and even more preferably less than 100kg/m². The advantage of such armor panels is that they provide the bestpossible AP and FSP protection with the lowest possible mass per unitarea. Thus, a composite panel according to the invention has a mass perunit area of less than 90 kg/m², or even less than 85 kg/m², it mightalso be possible to achieve protection level 5 defined in STANAG 4569(V50FSP=960 m/s with a 20 mm calibre projectile fired from 25 m).

The aluminium alloy plate includes one face oriented towards theprojectiles that may receive the impact directly, or that on thecontrary may be protected for example by ceramic tiles. It includes oneface opposite said face oriented towards the projectiles that is coveredby a composite reinforcing layer although there is not necessarily acontinuous bond over the entire contact surface, for example by means ofan adhesive binder. For example, all that is necessary is that thecomposite reinforcing layer is kept fixed to the plate around theperiphery of the plate by gluing or any other attachment means,typically mechanical.

We carried out AP and FSP tests on aluminium alloy plates coated or notcoated with a composite reinforcing layer comprising aramid fibres. APperforation tests use 7.62 mm calibre and 35.6 mm long projectilescalled “0.30 cal AP M2” that have a steel core, an intermediate leadlayer and a copper ogive casing. For the panels according to theinvention and the panels for which comparative tests were carried out,FSP tests use 23 mm long steel projectiles called “20 mm FSP”, thecylindrical part of which is 20 mm in diameter.

We observed firstly that in the target range of mass per unit area (50to 125 kg/m²), the results of perforation tests on the tested panelstructures (plates from 19 to 46 mm thick, panels between 30 and 50 mmthick, ratio of the weight of the composite reinforcing layer/totalpanel weight less than 25%), depended essentially on the alloy of theplate and the mean mass per unit area of the composite panel: a panelmade of a given uncoated alloy gives a result (expressed by the velocityV50) practically identical to the result for a panel composed of thesame alloy but thinner and coated with a composite reinforcing layerwith a thickness such that the assembly has the same mass per unit area.A slight deterioration of AP properties was even observed when the ratioby weight of the layer of composite stiffener/total weight of the panelis less than of the order of 22%. Thus, considering only the criterionfor resistance to perforation, an uncoated plate has a significanteconomic advantage and is smaller for exactly the same or even betterperformance. Among tested materials, aluminium alloys in the 7xxx seriesgive better results than alloys in the 5xxx and 6xxx series and steelsfor a comparable mass per unit area.

The results of FSP tests led to a different and surprising finding. Theapplicant observed that if plates are covered with a compositereinforcing layer comprising reinforcing fibres or bands with a highballistic protection capability, for example made of aramid fibres, witha mass per unit area more than 0.5 kg/m², preferably 1 kg/m², and evenmore preferably 2 kg/m², the gain in terms of an increase in V50 as afunction of the increase in the mass per unit area of the armor panel,is significantly more for aluminium alloys and particularly for alloysin the 7xxx series.

However, the best AP-FSP compromise is obtained with alloys in the 7xxxseries that have a sufficiently high content of zinc and copper. Thus7039 and 7020, if they are present, associated with a compositereinforcing layer of aramid fibres, have significantly improved FSPperformances, but have a relatively poor performance in AP perforationtests.

Thus, the alloy for the plate according to the invention has thefollowing composition, in which contents are expressed in percentages byweight:

5.1%≦Zn≦9.7% preferably 7.5%≦Zn≦8.7%.

1.5%≦Mg≦2.9% preferably 1.8%≦Mg≦2.7%.

1.2%≦Cu≦2.1% preferably 1.4%≦Cu≦2.1%

Si≦0.4% preferably Si≦0.12%

Fe≦0.5% preferably Fe≦0.15%

Mn≦0.3% preferably Mn≦0.2%

Cr≦0.28% preferably Cr≦0.05%

Ti≦0.2% preferably Ti≦0.05%

Zr≦0.15% preferably Zr≦0.05%

other elements≦0.05% individually and≦0.15% total.

Preferably, these alloys are treated to obtain a state not only withhigh instantaneous mechanical properties (strength UTS, conventionalyield stress TYS, elongation at failure E %) but also good toughness.Advantageously, a solution treatment will be carried out followed byquenching and annealing to obtain states such as T6 (maximum UTS), T64(quenched slightly under-annealed state), or preferably T651 (relaxedquenched by controlled moderate tension and annealing) or even T7651(relaxed quenched by controlled moderate tension and over-annealing).

In practice, the mass per unit area of the composite reinforcing layeris between 2 and 25 kg/m². It is preferably less than 20 kg/m², evenmore preferably less than 15 kg/m² mainly due to the cost.

The effect of this composite reinforcing layer on improvement of FSPproperties is certainly more accentuated when the mass per unit area ofthe composite reinforcing layer is high, but it is remarkable that thiseffect that becomes manifest with aluminium alloy plates, particularlyplates composed of the alloy according to the invention, even if thecomposite reinforcing layer is thin with a mass per unit area of theorder of 1 kg/m², in other words as soon as the panel is coated withthree or four woven aramid fabrics.

When the mass per unit area is less than 90 kg/m², aluminium alloys suchas 7xxx have FSP performances lower than the performances of a steel forarmor shielding, such as HHS (“high hardness steel”). But when thesealloys are combined with a composite reinforcing layer comprising aramidfibres, the FSP results are quickly better than the results for steel,even if the steel is covered with the same type of composite reinforcinglayer with a comparable mass per unit area. For example, to obtain thesame improvement of FSP performances on a steel plate as is observed on7xxx plates with a composite reinforcing layer with a mass per unit areaequal to only 2 kg/m², said steel plate needs to be associated with acomposite reinforcing layer between 4 and 6 times thicker, all otherthings being equal.

The effect of the composite reinforcing layer on the improvement of FSPproperties is particularly remarkable when the plate is 7449 T651.

Among the different tested composite reinforcing layers, the layercomposed of a stack of woven fabrics using Kevlar® 129 threads gave goodresults regardless of the type of weaving made. Kevlar® 129 grade isknown for its lightweight and its high mechanical performances andparticularly its high toughness.

7449 T651 plates covered with fabric layers woven from Kevlar® 129threads have the best AP and FSP performances. This alloy can give a V50for the FSP test greater than 950 m/s with an armor panel for which theglobal mass per unit area is less than 95 kg/m², or even less than 90kg/m².

FIG. 1 shows the results of AP tests carried out on shielding panelscomposed of metal plates coated or not coated with a compositereinforcing layer comprising aramid fibres.

FIG. 2 shows the results of FSP tests carried out on armor panelscomposed of aluminium alloy plates in the 7xxx series and made of steel,coated or not coated with a composite reinforcing layer comprisingaramid fibres.

FIG. 3 shows the improvement of FSP properties in terms of relativevariation of V50 as a function of the increase in mass per unit area,for several materials.

FIG. 4 shows the improvement of FSP properties in terms of animprovement of V50 as a function of the increase in mass per unit areadue to the composite reinforcing layer, for several materials.

EXAMPLE

Armor plates were made from thick plates made of different alloys. Theywere machined to different thicknesses between 25 and 40 mm. Table 1shows the main constituents of their chemical compositions.

TABLE 1 Alloy Type Si Fe Cu Mg Zn A 7449 0.05 0.07 1.9 2.1 8.5 B 60610.62 0.4 0.26 1.0 0.00 C 7020 0.13 0.12 0.13 1.22 4.69 D 0.05 0.07 1.72.0 9.4

Table 2 shows the state, thickness and average mechanical properties ofthese plates (tension, transverse longitudinal direction).

TABLE 2 Rp0.2 Rm Alloy State Thickness (MPa) (MPa) A % A T651 30 583 65111 B T6 30 295 330 12 C T651 30 360 420 12 D SHT 472° C.- 25 694 70711.5 quenched-6 h 120° C. + 7 h 135° C.

Some plates were covered with a composite reinforcing layer comprising astack of a various number of fabrics woven in threads based on Kevlar®129 fibres with a linear density of 1330 dtex, coated with polyvinylbutiral (PVB) resin, each fabric having a mass per unit area of about275 g/m². Composite reinforcing layers with different thicknesses weremade by stacking a variable number of fabrics, and the stack was thenhot compressed in a press.

Ballistic perforation tests (“AP tests”) Table 3 contains the results of“0.30 cal AP M2” tests carried out on thick plates coated or not coatedwith a composite reinforcing layer. When there was a compositereinforcing layer, it was placed on the side opposite the projectile.The mass per unit area of the stack of fabrics woven from Kevlar® 129threads is given in the fourth column in table 3 below.

FIG. 1 shows the different results obtained and compares then withresults known on other materials (5083 H131 (MIL-DTL-46027); RHA Steel(MIL-A-12560); 7039 T64 (MIL-DTL-46063), 6061 T651 (MIL-DTL-32262)).

It is found that for masses per unit area typically less than 100 kg/m²,the performances of 5083 and 6061 alloys are not as good as theperformances of steels such as RHA Steel, which has a lower performancethan 7449. AP performances of 7039 plates relative to the mass per unitarea are hardly better than steel and significantly lower than 7449.Known AP tests on the 7020 alloy were made with a different projectileand the results are not directly comparable. However, they show that theAP performances of 7020 are not better and are rather worse that theresults of 7039.

Once the thick 7449 plates have been coated with woven fabric made ofKevlar® 129 threads, their behaviour is similar or slightly less goodthan uncoated thick plates, for equal mass per unit area.

TABLE 3 Stack of layers woven from Kevlar ® 129 threads Mass per Massper Test Thickness unit area unit area V50 piece Alloy (mm) (kg/m²) Glue(kg/m²) (m/s) 1-1 7449 T651 30 0 0 85.5 805 1-2 7449 T651 30 0 0 85.5815 1-3 7449 T651 30 16.7 1 102 862 1-4 7449 T651 30 10.7 1 96 844 1-57449 T651 30 10.7 0 96 845 1-6 7449 T651 30 22.9 0 108 876 1-7 7449 T65139.3 0 0 112 948 1-8 7449 T651 39.9 0 0 114 944 1-9 7449 T651 39.9 0 0114 936 1-10 7449 T651 39.9 0 0 114 877 1-11 7449 T651 25.5 0 0 73 7241-12 7449 T651 19 0 0 55 612 1-13 6061 T6  30 0 0 81 641 1-14 6061 T6 30 16.7 1 98 702 1-15 6061 T6  30 22.9 1 104 767

FSP Tests

Table 4 contains the results of the “20 mm FSP” tests carried out onthick plates coated or not coated with a composite reinforcing layer.When there was a composite reinforcing layer, it was placed on the faceopposite the face that will receive the impact of the projectile.

FIG. 2 shows the different results obtained on 7020, 7449 and a highhardness steel (HHS) with a Brinell hardness of between 420 and 480 HB.These results are compared with the results obtained on other materials(7039 T64 (MIL-DTL-46063), RHA Steel (MIL-A-12560)). FIG. 2 alsocompares the results obtained for coated and uncoated 7xxx plates, andcoated and uncoated steel plates.

FIG. 2 shows that the performance of uncoated steel plates is higher forFSP tests than aluminium alloy plates, as long as the mass per unit arearemains less than about 100 kg/m².

TABLE 4 Composite reinforcing layer Mass per Test Thickness unit areaMass per V50 piece Alloy (mm) (kg/m²) Glue unit area (m/s) 2-1 7449 T65130 0 0 85.5 534 2-2 7449 T651 39.3 0 0 112 827 2-3 7449 T651 39.9 0 0114 842 2-4 7449 T651 39.9 0 0 114 884 2-5 7449 T651 39.9 0 0 114 8772-6 7449 T651 30 3.9 1 89.4 837 2-7 7449 T651 30 7.7 1 93.2 942 2-8 7449T651 30.8 10.7 1 98.5 1102 2-9 7020 T651 28.5 0 0 79.1 534 2-10 7020T651 30.75 0 0 85.3 600 2-11 7020 T651 30.75 3.9 1 89.2 834 2-12 HHS 1010.7 1 89.3 812 2-13 HHS 10 0 0 78.6 585

Experimental points obtained with uncoated 7449 T651 show a trend curveparallel to curve for 7039 T64, but with slighter lower FSPperformances. Experimental points obtained with 7020 T651 are also on atrend curve approximately parallel to the curve for 7039 T64 but withslightly higher FSP performances. The experimental point of uncoated HHSsteel plate is slightly below the trend curve for “RHA Steel”.

Points for 7449 T651 plates coated with a composite reinforcing layercomprising aramid fibres are significantly higher than the curve thatcontains the FSP results for uncoated plates. The difference,significant even with a thin coat, is greater when the compositereinforcing layer is thicker. Thus, the combination of a 7449 T651 platewith a composite reinforcing layer comprising Kevlar® 129 fibres with amass per unit area of 10.7 kg/m² can give a V50 of more than 1100 m/s

The results for the coated 7020 T651 plate also show the significantinfluence of the composite reinforcing layer. This appears neverthelesslower than that observed on 7449 plates. Furthermore, known AP resultson the 7020 alloy suggest that alloys with low copper content such as7020 and 7039, even associated with a composite reinforcing layercomprising aramid fibres, cannot give a good AP-FSP compromise.

The FSP results for the coated steel plate also show an influence of thecomposite reinforcing layer, but this is significantly lower.

Table 5 shows FSP results on coated aluminium alloy plates and estimatesthe gains obtained in comparison with uncoated plates. For eachcomposite panel, the 6^(th) column contains the results obtained for theuncoated plate A composed of the same material as the core of thecomposite panel and with the same thickness as the composite panel, andthe 7^(th) column contains estimated values for an uncoated plate Bcomposed of the same material as the core of the composite panel andwith the same mass per unit area as the composite panel. It can be seenthat the gain due to the presence of the composite reinforcing layerexpressed in terms of an increase of V50, is higher by a factor ofbetween 4.8 and 7.8 for aluminium alloys. This coefficient is of theorder of 6.6 for aluminium alloy and only of 4.5 for steel, for the samethickness of the composite reinforcing layer.

FIG. 3 shows these same results in the form of a relative increase inV50 as a function of the relative increase in the mass per unit area.Thick curves are associated with 7449. Curve (I), that is approximatelystraight and has a low gradient, represents the effect of the increasein the thickness of uncoated plates on the relative increase of V50.Curve (II) shows the effect of increasing the thickness of the compositereinforcing layer in the composite panels on the relative increase ofV50.

TABLE 5 Core Panel mass Core mass Gain thick- per unit per unit V50 GainV50 Test ness area V50 area V50 A V50 B B − A Composite-A piece (mm)(kg/m²) (m/s) (kg/m²) (m/s) (m/s) (m/s) (m/s) Factor 2-6 30 89.4 83785.5 534 577 43 303 7.0 2-7 30 93.2 942 85.5 534 620 86 408 4.8 2-8 30.898.5 1102 87.8 603 679 76 499 6.6 2-11 30.8 89.2 834 85.3 600 641 41 2345.7 2-13 10 89.3 812 78.6 585 635 50 227 4.5

For example, it can be seen in FIG. 3 that a relative increase of 10% inthe mass per unit area of the 7449 T651 armor panel, leads to a relativeincrease in FSP performances of the order of 20% if all that is done isto increase the panel thickness, and of the order of 80% if a compositereinforcing layer comprising aramid fibres is associated with it. TheFSP performances of composite panels with a 7020 core are alsosignificant. Performances are more modest when the panel core is made ofsteel (dashed lines curve).

FIG. 4 shows the gain in V50 as a function of the increase in mass perunit area. The effect of the composite reinforcing layer on theimprovement of FSP properties is very clear even if the compositereinforcing layer is thin, once the mass per unit area of said compositereinforcing layer is greater than a value of the order of 1 kg/m², whichtypically corresponds to a stack of at least five fabrics woven fromaramid thread. It can also be seen that to obtain the same improvementin FSP performances as is observed in 7xxx plates with a compositereinforcing layer with a mass per unit area equal to only 2 kg/m² on asteel plate, said steel plate must be associated with a compositereinforcing layer between 4 and 6 times thicker, all other things beingequal.

Finally, an analysis of the results leads to the conclusion thatprotection level 5 as defined in standard STANAG 4569 [V50 greater than960 m/s for 20 mm FSP tests] can be obtained with a composite panel madeof an aluminium alloy with the composition coated by a compositereinforcing layer containing aramid fibres with a mass per unit area ofless than 95 kg/m².

1. Armor panel comprising an aluminium alloy plate wherein: a) saidaluminium alloy has the following chemical composition expressed inpercentages per weight: 5.1%≦Zn≦9.7% 1.5%≦Mg≦2.9% 1.2%≦Cu≦2.1% Si≦0.4%Fe≦0.5% Mn≦0.3% Cr≦0.28% Ti≦0.2% Zr≦0.15% b) said plate comprises a faceadapted to be oriented towards a projectile and a face opposite saidface adapted to be oriented towards a projectile coated with a compositereinforcing layer comprising reinforcing fibres or bands with highmechanical performance that confers a high ballistic protectioncapability on them.
 2. Armor panel according to claim 1, wherein thereinforcing fibres or bands with a high ballistic protection capabilitymay be made from one or more materials selected from the groupconsisting of: glass with high mechanical performance optionally R, H, Sglass or optionally S2 glass; aramids, optionally para-aramids; HighPerformance PolyEthylenes (HPPE) or Ultra-High Molecular WeightPolyEthylenes (UHMWPE or UHMW).
 3. Armor panel according to claim 1,wherein said composite reinforcing layer comprises one or optionallymore single-directional or woven fabrics made from threads comprisingfibres with a high ballistic protection capability.
 4. Armor panelaccording to claim 3 in which said composite reinforcing layer comprisesfabric woven from para-aramid threads impregnated with resin.
 5. Armorpanel according to claim 4, in which said resin is a modified PVB(polyvinyl butyral) phenolic resin.
 6. Armor panel according to claim 1,in which the composite reinforcing layer is a stack of hot compressedfabrics.
 7. Armor panel according to claim 1, having a thickness of atleast 5 mm and at most 50 mm and a mass per unit area of at most 125kg/m².
 8. Armor panel according to claim 7, having a thickness of atleast 20 mm and at most 40 mm and a mass per unit area of at most 110kg/m², and optionally at most 100 kg/m².
 9. Armor panel according toclaim 1, wherein the mass per unit area of the composite reinforcinglayer comprising aramid fibres represents not more than 25%, optionallynot more than 15% of the total mass per unit area of the panel. 10.Armor panel according to claim 1, wherein the mass per unit area of thecomposite reinforcing layer comprising aramid fibres is at least 0.5kg/m², optionally 1 kg/m², and/or optionally 2 kg/m².
 11. Armor panelaccording to claim 1, wherein mass per unit area of the compositereinforcing layer comprising aramid fibres is at most 25 kg/m²,optionally 20 kg/m², and/or optionally 15 kg/m².
 12. Armor panelaccording to claim 1, wherein said plate is made from 7449 alloy,optionally in T651 state.
 13. Armor panel according to claim 1, whereinsaid composite reinforcing layer comprises one or more woven fabricsusing Kevlar® 129 coated with polyvinyl butyral (PVB) resin.